Fig 1.
Capture locations of Raja brachyura, Raja clavata, and Raja montagui.
Samples were collected between June 2018 and March 2024. Locations were estimated from the national fisheries catch and effort database by linking fish landings with fishing trip locations and visualised using the “rnaturalearth” package in R version 4.4.1.
Fig 2.
Example images of vertebral centra for each preparation method.
Anterior whole stained (A), posterior whole stained (B), anterior whole unstained (C), posterior whole unstained (D), anterior sectioned stained (E), posterior sectioned stained (F), anterior sectioned unstained (G), posterior sectioned unstained (H) from Raja brachyura. Images C and D were from a were from an 85.2 cm LT female caught in January 2022, all other images were from a 103.7 cm LT male caught in May 2023. Annual growth rings with complete opaque bands were annotated, with the birthmark indicated by an arrow.
Fig 3.
Schematic representing the 2 x 2 x 2 factorial design.
Vertebrae from the same individual were used in one or more of the preparation methods described. Differences in the age estimations for each treatment were tested using a Mann–Whitney–Wilcoxon test. This experimental design was applied consistently across all species: Raja brachyura, Raja clavata, and Raja montagui.
Table 1.
Total number of samples generated for each vertebral preparation method.
Table 2.
Summary of ageing precision results of each vertebral preparation method.
Fig 4.
Age bias plots comparing modal age estimations (years) between different vertebral preparation methods.
Anterior, sectioned, stained vertebrae and anterior, whole, stained vertebrae (A–C); posterior, sectioned, stained vertebrae and posterior, whole, stained vertebrae (D–F); anterior, whole, stained vertebrae and posterior, whole, stained vertebrae (G–I); anterior, sectioned, stained vertebrae and posterior, sectioned, stained vertebrae (J–L), for Raja brachyura, Raja clavata and Raja montagui. Significance was tested using a Mann–Whitney–Wilcoxon test where W is the test statistic.
Fig 5.
Age bias plots comparing modal age estimations (years) between stained and unstained vertebral preparation methods.
Anterior, whole, stained vertebrae and anterior, whole, unstained vertebrae (A–C); anterior, sectioned, stained vertebrae and anterior, sectioned, unstained vertebrae (D–F); posterior, sectioned, stained vertebrae and caudal, sectioned, unstained vertebrae (G–I); posterior, whole, stained vertebrae and posterior, whole, unstained vertebrae (J–K), for Raja brachyura, Raja clavata and Raja montagui. Significance was tested using a Mann–Whitney–Wilcoxon test, where W is the test statistic.
Table 3.
Growth parameters (mean ± 95% confidence interval) calculated for Raja brachyura, Raja clavata, and Raja montagui.
Fig 6.
Von Bertalanffy growth curves.
Constructed using age-at-length data derived from whole, stained vertebrae collected from both anterior and posterior vertebral locations for (A) Raja brachyura, (B) Raja clavata, and (C) Raja montagui.
Table 4.
PCA values of all vertebral preparation methods for the three skate species Raja brachyura, Raja clavata and Raja montagui.
Table 5.
PCA values calculated concerning vertebral location of whole, sectioned and stained vertebrae for each of the three skate species Raja brachyura, Raja clavata, and Raja montagui.
Table 6.
PCA values calculated concerning vertebral structure of anterior, stained vertebrae for each of the three skate species Raja brachyura, Raja clavata and Raja montagui.
Table 7.
PCA values calculated concerning vertebral staining of anterior, whole vertebrae for each of the three skate species Raja brachyura, Raja clavata and Raja montagui.
Fig 7.
PCA plot visually representing the three species; Raja brachyura, Raja clavata, and Raja montagui.
Ellipses show 95% confidence intervals.
Fig 8.
PCA plot visually representing differences between vertebral location for the three species (A) Raja brachyura, (B) Raja clavata, and (C) Raja montagui.
Ellipses show 95% confidence intervals.
Fig 9.
PCA plot visually representing differences between vertebral structure for the three species (A) Raja brachyura, (B) Raja clavata, and (C) Raja montagui.
Ellipses show 95% confidence intervals.
Fig 10.
PCA plot visually representing differences between vertebral staining for the three species (A) Raja brachyura, (B) Raja clavata, and (C) Raja montagui.
Ellipses show 95% confidence intervals.